1. Field of the Invention
The present invention relates to an electronic exchange having a function of a Calling Number Delivery (hereinafter, abbreviated to CND) service and a function of a Calling Number Delivery Blocking (hereinafter, abbreviated to CNDB) service and performing a switching between a call originating subscriber and a call terminating subscriber.
According to a specification by, for example, Bellcore for the North American market, varieties of class services are defined. For example,
SCF=Selective Call Forwarding PA1 SCR=Selective Call Rejection PA1 COT=Customer Originated Trace PA1 AC=Automatic Call Back PA1 AR=Automatic Recall PA1 DRCW=Distinctive Ringing Call Waiting and the aforementioned CND, CNDB and so on. The present invention intends to present a proposal for an improvement of, among the above recited services, the CND service and the CNDB service. Here, the CNDB service is a service for indicating a telephone number of a call originating subscriber to a call terminating subscriber. Namely, a call terminating subscriber can see, before taking his telephone off-hook, the telephone number of a call originating subscriber on a display mounted on a part of the telephone. Therefore, a service is given by which a terminating subscriber can reject beforehand, during ringing, a call originated from a subscriber which is not wanted by the call terminating subscriber.
On the other hand, the aforesaid CNDB service exists, which service makes a pair with the aforesaid CND service. The CNDB service is a service, when the call terminating subscriber is registered in advance as a person who is allowed to use the CND service, which can block indication of the own (call originating subscriber) telephone number on a display at the call terminating subscriber side. Namely, even if the call terminating subscriber is allowed to use the CND service, this call terminating subscriber cannot see a telephone number of the other party (call originating subscriber). Therefore, a service is given which can minimize the possibility of a rejection by the other party (call terminating subscriber) if the call is not wanted by the terminating party.
2. Description of the Related Art
As will be explained later with reference to the attached drawing, there were at least the following two problems:
(1) It is troublesome, for the call originating subscribers registered to use the CNDB service, to do an operation, i.e., a dialing of an access code, at all time for blocking an indication of a telephone number so long as it is not evident, in advance, that the other party is not registered to use the CND service.
(2) If a call originating party forgets to do the operation for blocking an indication of a telephone number, the own telephone number is inevitably indicated at the telephone terminal of the other party.